horizontal

adjective

being in a prone or supine position; recumbent: His bad back has kept him horizontal for a week.

near, on, or parallel to the horizon.

of or relating to the horizon.

measured or contained in a plane parallel to the horizon: a horizontal distance.

(of material on a printed page, pieces on a game board, etc.) extending across, from the left to the right of the viewer.

of or relating to a position or individual of similar status: He received a horizontal promotion to a different department, retaining his old salary and title.

Economics. of or relating to companies, affiliates, divisions, etc., that perform the same or similar functions or produce the same or similar products: Through horizontal mergers the company monopolized its field.